Lois G. Lerner, the former Internal Revenue Service official at the center of the tea party targeting scandal, expressed contempt for conservatives and called them “a—holes” in newly discovered emails, fueling a drive by House Republicans for a special counsel to investigate the tax agency.

The email was among a batch of evidence that House Ways and Means Committee Chairman Dave Camp, Michigan Republican, turned over Wednesday to the Justice Department in support of an investigation into criminal wrongdoing at the IRS.

In the Nov. 9, 2012, email exchange from Ms. Lerner’s official IRS email account, she demonstrates “deep animus towards conservatives, which she refers to as “–holes,” Mr. Camp said.

In other emails, Ms. Lerner appeared to refer to conservatives as “crazies.”

“Despite the serious investigation and evidence this committee has undertaken into the IRS’s targeting of individuals for their beliefs, there is no indication that [the Justice Department] is taking this matter seriously,” Mr. Camp said in a letter to the department. “In light of this new information, I hope DOJ will aggressively pursue this case and finally appoint a special counsel, so the full truth can be revealed and justice is served.”

The IRS has admitted that some of its field agents wrongly targeted tea party and other conservative groups for extra scrutiny when they applied for tax-exempt status. But the agency has maintained that the targeting and delays were not organized efforts or politically motivated.

The newly disclosed emails were not from the critical time period from 2009 to 2011, when the IRS claims messages were lost when Ms. Lerner’s computer crashed.

In one email highlighted by the committee, she wrote, apparently referring to conservative critics of the administration: “So we don’t need to worry about alien teRrorists (sic). It’s our own crazies that will take us down.”

In another passage, she replies to a friend bemoaning the negative critiques of President Obama and administration policy on talk radio shows. Ms. Lerner responds: “Great. Maybe we are through if there are that many a—holes.”

Other emails showed that Ms. Lerner used her personal home computer for IRS business and may have stored taxpayer information.

An email she sent Feb. 22, 2012, to an IRS information technology specialist had the message line: “Virus on Home PC.”

In the exchange, Ms. Lerner indicated that she kept work information on her home computer and some of it may have been lost.

She said her computer may have been “simply hacked because my password was too simple.”

Mr. Camp said the messages overall heighten concerns that taxpayer information may have been leaked.

Ms. Lerner retired from the agency last year while under scrutiny for her actions.

The House has since voted to hold Ms. Lerner in contempt of Congress for refusing to testify under oath. Her attorney has said she did not break the law but doesn’t trust the congressional investigation.

The latest emails emerged as the House Judiciary Committee heard testimony on the merits of appointing a special counsel to investigate the IRS.

Republicans say the Obama administration cannot be trusted to investigate itself on such a sensitive question. President Obama has declared that there was not a “smidgen” of evidence linking any IRS misdeeds to political interference by the White House.

The House passed a resolution in May calling on Attorney General Eric H. Holder Jr. to name a special prosecutor. Mr. Holder is the only one empowered to name a special prosecutor, but he has refused to do so. He has said an investigation his department is conducting is sufficient.

Jay Sekulow, chief counsel of the American Center for Law and Justice, which represents dozens of conservative groups targeted by the IRS, told the committee that the Justice Department is conducting a “faux investigation.”

“That there is a need for a special counsel. We’re never going to get to the bottom of this in civil litigation. That is going to take an outside counsel,” he said.

However, the only way for the Republican-run House to compel Mr. Holder to act would be by passing legislation that almost certainly would die in the Democrat-run Senate.

“The House’s quest for a special counsel is unrealistic,” testified Charles Tiefer, a professor at University of Baltimore School of Law.